Background: Recent, large randomized controlled trials focusing on depression treatment alone among persons with diabetes and heart disease have failed to show improved cardiovascular or diabetes outcomes. Benefits for depression outcomes have been variable in these trials, as cardiovascular disease and diabetes are also correlated with less favorable depression prognosis. An integrated approach may be needed to improve both depression and medical outcomes. Research goal: We propose to test a Chronic Disease-Focused Depression Treatment model enhancing both major depression and co-morbid chronic disease management in patients with poor disease control. We will test this intervention in a complex and difficult to treat patient population: depressed patients with poorly controlled diabetes and/or coronary heart disease (CHD). If we find that disease-focused depression treatment improves depression, chronic disease, and disability outcomes, it will accelerate adoption of evidence-based depression care for patients in general medical settings. Theoretical framework: This research will test Piette's conceptual framework for managing depression and comorbid chronic disease, emphasizing reciprocal effects of depression and chronic disease. Study design: Disease-Focused Depression Treatment will be assessed through a randomized controlled trial in which 300 persons with poorly controlled diabetes or CHD and major depression/dysthymia are assigned to either: 1) a depression treatment program that addresses management of comorbid disease;or 2) care as usual. We will screen 6400 persons with poorly controlled diabetes and/or CHD (blood pressure, glycemic, lipid dyscontrol) for depression and enroll 300 of these patients in the trial. Primary and secondary outcomes: We will evaluate the effectiveness over a 2-year period of Chronic Disease-Focused Depression Treatment for patients with depression and co-morbid diabetes and/or CHD who are poorly controlled. The primary measures of effectiveness of Disease-Focused Depression Treatment, relative to a usual care, will be effects on depressive symptoms and the percentage of patients with successful management of all three disease control measures (glycemic, blood pressure and lipid control). Secondary process and outcome measures will include functional disability, adherence to prescribed medications and disease self-management behaviors (i.e. physical activity and nutrition).